The biggest avalanche cycle of the season is underway now, with Highways 93 South and North closed through Saturday. Our recommendation is to stay out of the backcountry.
Mount Stephen Avalanche Closure Zone is CLOSED on March 20 for avalanche control.
Strong to extreme winds plus warmth and ongoing snowfall at higher elevations will continue to form widespread wind slabs at treeline and above.
A layer of facets and/or surface hoar is buried 50–120 cm deep. Warm temperatures and additional load from new precipitation and wind will make this problem very active over the next few days. We expect large and destructive avalanches reaching the end of historical runouts.
Extreme winds, warmth, and rain are initiating Loose Wet avalanches at TL and below, and Loose Dry avalanches in the ALP. Slab avalanches starting at high elevations will dig down into the wet snow at lower elevations, producing slow-flowing, loose wet avalanches. Avoid all avalanche terrain.
A widespread avalanche cycle is underway with large natural avalanches running into the runout zones. We expect larger avalanches to occur on Thursday and Friday as the storm progresses.
30-50 mm of precipitation has fallen since the storm began, which translates into roughly 50-70 cm of snow at higher elevations, combined with steady south winds of 60-100 km/hr. The rain line is about 2200 m. This storm is overloading the snowpack, and avalanches are releasing naturally persistent weak layers and potentially running on the ground at low elevations where the rain has turned the snowpack isothermal. This is the climax avalanche cycle of the winter.
A major Atmospheric River is pumping the moisture directly through this region from now until Friday night. Temperatures are warm, with freezing levels forecast to range from 2200 to 2500 m; winds are Extreme with gusts exceeding 100 km/hr from the SW; and 30-80mm of precipitation will fall before the storm ends.
